A cache of unpublished letters from the novelist Virginia Woolf and scores of first editions inscribed by leading writers and poets of the early 20th century has emerged in the contents of the library of Lady Ottoline Morrell, the society hostess who became one of the most flamboyant, loved and mocked associates of the Bloomsbury group.

Lady Ottoline was extremely well connected - her first cousin was Elizabeth Bowes Lyon, the future Queen Mother - and her friendships and affairs were legendary in her day and since. Her unmistakable figure, six foot tall with flaming red hair and usually dressed as flamboyantly as a parrot, stalks through books and works of art of the period.

The archive - which includes hundreds of books, many rare first editions, letters, photographs and paintings including a grim series of first world war scenes by the poet Siegfried Sassoon - has remained in her family since her death in 1938, but is to be sold next month at a Christie's auction.

She kept open house in London and at Garsington, her Jacobean mansion in Oxfordshire, and many treated her homes almost as a club.

Her drawing rooms were full of famous men, many of them her lovers.

Among the letters to be sold is one to her from Woolf. "I hate being a passive bucket," she wrote. "In short, great men bore me to death."

Woolf wondered: "How on earth does Ottoline suck enough nourishment out of the solitary male? I was thinking of your tea parties and I thought of Stephen Spender talking about himself and of old Tom [TS] Eliot also enlarging on the same theme and then in comes shall we say Siegfried [Sassoon] and it all begins again. Now in human intercourse I like the light to strike on more angles than one. And all clever men become frozen stalactites."

The clever men also included the philosopher Bertrand Russell, Roger Fry whom she helped choose pictures for his Post Impressionist exhibition, one of the most influential of the 20th century, WB Yeats - whom her other poets might have been dismayed to know she regarded as the only genius - Henry James, DH Lawrence, Winston Churchill and Herbert Asquith. There were also friends of her Liberal MP husband and almost all the Bloomsburies.

She was bisexual and her many, often unhappy, affairs included Fry, the painters Augustus John and Dora Carrington - who would kill herself after the death of her adored but resolutely homosexual Lytton Strachey, author Axel Munthe, and Russell.

She and Russell were friends after passion waned. He wrote of their first encounter: "For external and accidental reasons I did not have full relations with Ottoline that evening but we agreed to become lovers as soon as possible."

Caricature

Many of her guests were more than happy to accept her hospitality, and then brutally caricature her in their work. She was mortified to appear, painfully recognisably, in at least a dozen novels, including books by Osbert Sitwell, Aldous Huxley and, most famously, as the domineering and foolish Hermione Roddice in Lawrence's Women in Love.

Some critics believe she was also the model for Lawrence's most famous heroine, Lady Chatterley. She didn't have sex in a woodshed, but her fling with "Tiger", a young stonemason who came to carve plinths for her garden statues, was an open secret among the pathologically gossipy Bloomsburies.

She was deeply wounded by Lawrence's portrayal, as was Woolf on her behalf. In another letter in the collection, she wrote: "I was so angry I could hardly finish his letters. There you were, sending him Shelley, beef tea, lending him cottages, taking his photograph on the steps at Garsington - oft stuffing gold into his pocket - off he goes, has out his fountain pen and - well, as I say I haven't read it."

However the archive suggests that Ottoline herself, notoriously the kindest heart and the softest touch in Bloomsbury, had already forgiven Lawrence.

Crispin Jackson, head of Christie's books and manuscripts department, said of Ottoline yesterday: "It was easy for people to mock her, but she truly tried to do good and to help people. She was a remarkable woman, a thrower of parties certainly but a friend to anyone in need, who made her house a centre of opposition to the Great War - Siegfried Sassoon was devoted to her, and with very good reason."

She was collecting authors to the end of her days: the sale includes an inscribed first edition of Graham Greene's dire 1925 first collection of verse, Babbling April.

Unlike many celebrity libraries, Ottoline's books bear all the marks of being read and re-read, some to the point of disintegration.

Ultimately Virginia Woolf tried to make amends. One of the most poignant letters in the collection was written to Ottoline's husband, Philip Morrell, after her death. It explains that she and Eliot are struggling with a poem as an inscription for her grave: "As we all said - can one give any idea of Ottoline on a slab?"

They settled on: "A brave spirit, unbroken, Delighting in beauty and goodness, And the love of her friends."

Backstory

The loose association of writers, artists and intellectuals came together in the early 20th century. One wit said they "lived in squares but loved in circles". It began at 46 Gordon Square in Bloomsbury, the London home of Virginia Woolf and Vanessa Bell. As well as the sisters' long-suffering spouses the group included Bell's lover, the painter Duncan Grant; Woolf's lover Vita Sackville West; bisexual economist Maynard Keynes; critic Roger Fry; and the painter Walter Sickert - whom the crime writer Patricia Cornwall has spent a small fortune trying to finger as Jack the Ripper.